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Cropduster
22nd Feb 2019, 23:45
Saw something in a sim the other day that got me thinking and would like others thoughts on it.
Scenario was a simple engine failure in cruise at a weight of about 300 tons. One crew member wanted to dump fuel to landing weight, one wanted to land at current weight to save fuel and environmental damage. Runway was long enough to theoretically allow landing without blowing the tires (but barely) and aircraft was WAT capable of single engine go around.
So while I was siding with the more conservative course of action, are there any certification or technical issues with an overweight single engine landing?

Thanks, Cropduster.

B2N2
23rd Feb 2019, 02:21
Dump the fuel and land below max weight.

extreme P
23rd Feb 2019, 03:45
Plan to land at the nearest suitable airport?

Chesty Morgan
23rd Feb 2019, 04:03
...doesn't mean land immediately.

extreme P
23rd Feb 2019, 04:10
...doesn't mean land immediately.

What does it mean then?

Chesty Morgan
23rd Feb 2019, 04:36
It means land at the nearest suitable airport.

When it says land immediately that means land immediately.

harrryw
23rd Feb 2019, 05:11
https://www.youtube.com/watch?v=zRxGEFWYPgM

stilton
23rd Feb 2019, 07:53
Our operations manual specifically prohibits
this, with an engine failure (time allowing) dump to max landing weight


Saving fuel in this situation is a non starter

dixi188
23rd Feb 2019, 09:42
Overweight landing only when you have no time to dump!
Why cook the brakes and tyres?

wiggy
23rd Feb 2019, 10:10
Overweight landing only when you have no time to dump!
Why cook the brakes and tyres?

FWIW I’ll throw this into the debate - one of “our” triples suffered an interesting engine (as in not just a run down) failure in the cruise recently, whilst well over FCOM max landing weight.

Diversion to nearest suitable commenced...fuel dumping commenced..at which point the Fuel jettison system failed.

After suitable review (nature of the engine failure, performance, etc) the crew made the decision to land above max landing weight.

All ended well, aircraft checked out for overweight landing, nothing adverse found
as a result of the landing but the engine was a mess.

Company completely supportive of crew actions/decisions.

safetypee
23rd Feb 2019, 13:40
No obvious certification reasons.
O-Wt landing would not be higher than max takeoff wt; brakes etc are certificated and tested for max wt RTO. Thus brakes and tyre care is not an issue; your are not going to have a quick turnaround !

Time wise; land as you judge the urgency of the situation; according to the situation as assessed, at that time by the people there.

Weight; reduce wt to maximise safety as judged by the landing distance margin vs possible need to make several approaches / divert. Don’t box yourself in to making a ‘first time’ approach and landing which probably has ‘not be done before’ - simulator may not count for much in a real emergency; the aircraft may be the same, you are not.

Dump for the ‘environment’ ! Only if woods / wild life, fish stocks, or fuel tanks are in the overrun area.
Relatives will not thank you for planning a ‘Green funeral’.

ManaAdaSystem
23rd Feb 2019, 17:36
Our operations manual specifically prohibits
this, with an engine failure (time allowing) dump to max landing weight


Saving fuel in this situation is a non starter


Interesting. So if you take off at max TOW, get an engine failure at rotation, your company tells you to hold on one engine while dumping fuel down to max landing weight?
I don’t fly the 777 so how much holding time will this take?
I’m not sure your local CAA/FAA will agree wih your company.

Or did I read you wrong? You would dump as much fuel as possible and land at whatever weight you end up with on your way to your diversion field? Which is what I imagine most pilots would do.

wiggy
23rd Feb 2019, 17:57
Given that on e.g. -300 you can be departing 90’ish tonnes above max landing weight I’m also pretty sure the CAA/FAA wouldn’t be too impressed with a once around the pattern and land for a simple engine failure either.

FlightDetent
23rd Feb 2019, 18:42
Yikes, what else would they like to see? Fly out 60 miles to a fuel dump racetrack, spend 25 mins there and come back, does not sound too smart.

The AC is certified for an RTO with about 1000 m remaining to the stop. After an engine fails we do our thing, put all of the runway in front of the nose again, and land the ailing bird. Is that scenario any different for a heavy?

If it will take off, you can land it - my predecessors claim to bring that rule of thumb directly from Seattle - a certification requirement they said.

With a cargo smoke warning, we would be landing PDQ as the safest course of action. I do not see how a -1 engine makes that a less professional choice.

Ready to be educated, FD.

Check Airman
23rd Feb 2019, 19:17
FWIW I’ll throw this into the debate - one of “our” triples suffered an interesting engine (as in not just a run down) failure in the cruise recently, whilst well over FCOM max landing weight.

Diversion to nearest suitable commenced...fuel dumping commenced..at which point the Fuel jettison system failed.

After suitable review (nature of the engine failure, performance, etc) the crew made the decision to land above max landing weight.

All ended well, aircraft checked out for overweight landing, nothing adverse found
as a result of the landing but the engine was a mess.

Company completely supportive of crew actions/decisions.


In fairness, with the jettison system inop, they didn't really have much of a choice, now did they? ;)

To add to the debate, what does the MEL say about having the jettison system inop? That may give some insight into what Boeing thinks.

Disclaimer- I've never flown an airplane capable of dumping fuel.

Good Business Sense
23rd Feb 2019, 19:58
FWIW I’ll throw this into the debate - one of “our” triples suffered an interesting engine (as in not just a run down) failure in the cruise recently, whilst well over FCOM max landing weight.

Diversion to nearest suitable commenced...fuel dumping commenced..at which point the Fuel jettison system failed.

After suitable review (nature of the engine failure, performance, etc) the crew made the decision to land above max landing weight.

All ended well, aircraft checked out for overweight landing, nothing adverse found
as a result of the landing but the engine was a mess.

Company completely supportive of crew actions/decisions.



Yep - keep doing sensible, safe things as you receive each challenge. If you can, it's good to avoid a high speed landing but you need to balance it all up with what else is going on.

A Cathay Pacific 747-400 taking-off out of the old Kai Tak airport in 1995, on runway 13 out to sea, had an engine blow up, remained on fire in a big way - Captain did a 180 and landed back on runway 31 at 400 tones with 421 on board (max take-off weight) - as they did the 180 the two guys in the back did the performance sums etc etc etc (know your charts well I guess) - all this in around 11 minutes. Amazing ! NEEDS MUST !

I always found the ROD on final approach at those high speeds scary :-)

clark y
23rd Feb 2019, 20:52
Personally, I don't like the idea of sitting in the sky in a 300t single engine aircraft any longer than I have to.

tdracer
23rd Feb 2019, 21:25
During certification, we look at something called "Return to Land" - basically there is a serious emergency shortly after a Max Weight TO (e.g. uncontrollable fire), and you need to land ASAP - significant fuel dumping is not an option. It may not be pretty, and you want the pilots to be on their 'A' game, but it's required to be possible (and safe) to do a MTOW landing at the departure airport (since you just left there at MTOW, it presumably has a reasonably long runway). This of course assumes that whatever went wrong didn't significantly affect landing/stopping distances.

Personally I've been on a enough overweight landings during flight testing that I don't really see it as being that big of deal so long as the pilots know what they're doing and you're not talking something like a short and/or contaminated/slick runway.

Good Business Sense
23rd Feb 2019, 21:59
Personally, I don't like the idea of sitting in the sky in a 300t single engine aircraft any longer than I have to.



I got used to it after the first couple of times !

wiggy
24th Feb 2019, 07:16
Boeing’s thoughts here, (probably based on some of the testing tdracer was involved in):

https://www.boeing.com/commercial/aeromagazine/articles/qtr_3_07/article_03_1.html

FlightDetent
24th Feb 2019, 12:56
I think the message of the article is quite clear.

HPSOV L
24th Feb 2019, 21:37
Agree.
If I am sitting down the back with my family I’d rather you didn’t climb up and fly off somewhere remote to spend 45 minutes dumping fuel on one engine if the aircraft has the ability to land immediately with ample performance margins.
Land at Nearest Suitable Airport implies a certain urgency due to lack of redundancy. Of course it may be safer to reduce the landing weight depending on the circumstances , so let’s not make absolute statements.

Cropduster
25th Feb 2019, 18:04
Thanks for all the replies, especially tdracer, and wiggy.
While we all know that the airplane can reject at take off weights so obviously it can land again, this is probably not something we want to do unless in a land immediately situation, Tires melted for sure, probably the brakes finished, and maybe even an evacuation due to a brake fire underneath all the fuel. I have seen some pretty dramatic videos of near V1 reject flight testing.

My own airline had a few cases of airplanes returning heavy after flap issues. The performance charts said it could be done, and it could (and was). The last one required the mechanics to cut the melted brakes off the axles. We were then issued non mandatory "guidance" that suggested dumping to max landing weight (or more if required) any time we were dealing with an aircraft problem. Obviously this requires flying around in circles for half an hour in the manner FlightDetent alluded to. And obviously you wouldn't do this if there was any doubt as to the integrity of the other engine or if something was on fire, but the risk of an apparently healthy ETOPS certified engine failing in a particular 30 minute period should be extremely remote. Our guidance will try and have us avoid dumping unnecessary fuel and land overweight if there is nothing wrong with the airplane and runway length permits.

I guess I can see the logic with this. An overweight landing requires a gentle(ish) touchdown in the touchdown zone to take advantage of all the available runway. An engine out, flap, or flight control issue introduces potential handling complications that could work against the objectives of the overweight landing. Why combine the two if you don't have to?

Anyway, we saw this in a sim scenario and I just wondered what the collective wisdom was. On the sim scenario in question, the matter was resolved by a pop up notam that reduced the useable runway length and required dumping fuel.

Cheers Cropduster.

ManaAdaSystem
25th Feb 2019, 18:12
There is a huge difference between holding on a single engine and holding on two good engines.

HPSOV L
25th Feb 2019, 23:09
It's a good subject Cropduster, and inevitably generates opposing opinions because there is truth on both sides.

I wonder if you are extending your companies guidance beyond it's original intent, which seems to relate to non-time critical problems (such as flaps)?
The ETOPs thing comes up quite a bit and it is true; engine reliability is such that you could argue that the balance of risk favours increasing the flight time rather than accepting the reduced margin for safety in a high energy landing. However it's not that simple:
I can think of a couple of cases off the top of my head where the "good" engine was discovered to have a problem on landing (eg LOT 787 diversion to JFK recently).
A properly planned overweight landing uses far less energy than the one in spectacular RTO certification videos as you have at least twice the available stopping distance and a thrust reverser. The brake fuses will probably deflate the tires but that is accepted as part of the aircraft design.
Jettisoning fuel may be problematic in environmentally sensitive areas. If you don't want to fly off to a remote designated fuel jettison area, you may have to invoke emergency authority. Which is fine but could you justify that if the performance was adequate to safely land overweight?
Boeing designed the thing to land above MLW in emergencies. FAR regs do not even require it to have a jettison system.

Having said all that, my philosophy is that if circumstances permit I will start fuel jettison as soon as possible and then do an unhurried set up for landing. I'll figure out the maximum acceptable landing weight during this time using a nice fat margin. The resulting landing may or may not be overweight.

tdracer
26th Feb 2019, 00:25
FAR regs do not even require it to have a jettison system.

Are you sure about that part? It may not be spelled out in the FARs, but good luck certifying without one if there is a big delta between MTOW and Max Landing.
At EIS, the 767 didn't have a fuel jettison - but Max TO was 330k lbs., and Max Landing was 320k lbs. - so no big deal. But then Boeing started jacking the max TO weight - eventually getting over 400k lbs., but max landing didn't change. The FAA mandated Boeing install a fuel jettison system, and even went so far as to force it be retrofit to a few already delivered aircraft.

HPSOV L
26th Feb 2019, 03:46
Pretty sure...

AERO - Overweight Landing? Fuel Jettison? What To Consider (http://www.boeing.com/commercial/aeromagazine/articles/qtr_3_07/article_03_2.html)

But who knows...in a big organization corporate memory can get pretty foggy.

zzuf
26th Feb 2019, 12:03
Are you sure about that part? It may not be spelled out in the FARs, but good luck certifying without one if there is a big delta between MTOW and Max Landing.
At EIS, the 767 didn't have a fuel jettison - but Max TO was 330k lbs., and Max Landing was 320k lbs. - so no big deal. But then Boeing started jacking the max TO weight - eventually getting over 400k lbs., but max landing didn't change. The FAA mandated Boeing install a fuel jettison system, and even went so far as to force it be retrofit to a few already delivered aircraft.

The requirement for a fuel jettison system depends on climb performance at MTOW not the MTOW MLW Delta. FAR 25.1001

B2N2
26th Feb 2019, 16:07
Why?
Back it up ol boy.

What is the the reason the donk failed. What do you do when the second fails - while dumping - while you send your beloved Acars to your ops .

Do you not brief these type of scenarios before take off.
Are you familiar with your AFM.



First of all I’m not your “old boy”.
Second I’m familiar with my AFM thank you.
Third we brief a catastrophic failure and immediate return and not the other 1327 scenarios.

Boeing prohibits auto land when overweight on the type I fly.
That may be an important consideration in the event of further cascading failures.
Your departure airport may not be the best choice to return to for a myriad of reasons.
An uncontained faikure followed by an uncontrollable fire would be a reason for immediate overweight return.
Anything else which may prevent you from continuing to your destination would require additional analysis and decision making which requires time.
The world famous Thompson bird incident caught on tape is a prime example as to why I would decide to dump fuel to land below max landing weight.

safetypee
26th Feb 2019, 17:36
Cropduster,
A lesson from this debate is not to invent concerns / scenarios or use unfounded ‘certainties’ or ‘guesses’ to justify a course of action.

Based on certification tests, tyres do not ‘melt’, rarely suffer blow outs (antiskid still works), but more likely the protective fusible plugs will deflate them.
Don’t believe all that you see on web videos. Were the tests shown certification successes or otherwise? Many of those RTOs could have been acceptable, which includes allowable deflating tyres and brake fires which must be ‘contained’ without intervention for 5 mins.
Fuel concerns, etc, in abnormal circumstances have been considered in certification, have been flown, and as necessary, demonstrated.
Brakes will be used up to their limit, there may be apparent fire, or brake damage … but that’s inconsequential to the safety decision in planning an overweight landing.

‘A gentle touchdown’; unless your normal landings are greater than 6 ft/sec, then an overweight landing can be flown as a normal landing.
Don’t invent new procedures where none are required.
Don’t create concerns which could distract from the choice of the safest course of action.

Yaw String
26th Feb 2019, 21:07
Or you could fly your A320 over London for nearly thirty minutes,minus its cowls,and then land with smoke coming from one!
Did anyone come up with the reason why that crew stayed airborne for so long?

If you've lost one,and there's asphalt long enough to take you,get it on the ground,and don't wait for SOD or his copilot,MURPHY, to get you by the short and curlies!..Or you could fly round and round in circles,talking to company,dumping fuel,and hope a large bird doesn't go down the other one!

t-bag
27th Feb 2019, 08:35
The world famous Thompson bird incident caught on tape is a prime example as to why I would decide to dump fuel to land below max landing weight.Well that was a 757 so they didn`t dump fuel - whats your point?

dixi188
27th Feb 2019, 12:47
Cloudtopper

Originally Posted by [b]dixi188 https://www.pprune.org/images/buttons/viewpost.gif (https://www.pprune.org/tech-log/618698-b777-single-engine-overweight-landing-question-post10398214.html#post10398214)
Overweight landing only when you have no time to dump!
Why cook the brakes and tyres?
please substantiate this reply .

Whilst the aircraft is certified to stop from V1 at Max T.O. weight, the wheels and brakes will almost certainly be cooked and tyres deflated. In an overweight landing with Max Autobrake selected, I think the result would be the similar.
I have only ever done these Max weight excercises in the Sim, but with Carbon brakes on the A300, the brake temps went off the scale, (over 700 degrees C). I don't see the B777 being very different.

Obviously, with the Fuel Dump inop. there is little choice but to land overweight, and with a long runway and lighter braking then the brakes could be saved.

My thoughts,

Dixi188

FlightDetent
28th Feb 2019, 10:35
Dixi188, the MTOW RTOW runs are done with brakes worn down to 25% and will cook them, as well as blow the tyres at the stop - it is a destructive test, agreed until this point. I haven't seen the numbers, so guessing here: the deceleration part eats about 1000 m.

The difference of opinions lies in how much of that actually applies for the overweight landing case in standard configuration. The approach speeds with landing flap tend to be 10% less than at liftoff, which alone provides a dramatic decrease of E(k) in the benefit of the return scenario. The pilots have all of the 3000m-ish runway at their disposal and there is no need to stop by the 1200 meters mark.

Thus our argument that destruction of the wheel assembly due to excessive braking energy does not enter the assessment matrix for an immediate landing at MTOW.

Daniel_11000
28th Feb 2019, 15:31
Boeing’s thoughts here, (probably based on some of the testing tdracer was involved in):

https://www.boeing.com/commercial/aeromagazine/articles/qtr_3_07/article_03_1.html

.... and the answer is :

FAR criteria require that landing gear design be based on:

-A sink rate of 10 feet per second at the maximum design landing weight; [...]

which equates to a touch-down vertical speed of 600 fpm !

However, in many AMM Ch 5 , the 'Overweight Landing' inspection is much reduced if the
vertical speed at touch-down is very low (FDR redout helps).
A high-vertical speed touch-down in overweight condition will surely make nasty damages to wing and/or LG
and/or other structure.

ASRAAMTOO
6th Mar 2019, 16:33
Let me throw another small hand grenade into the discussion. Imagine that your company policy is not to land overweight unless it would be dangerous not to. Imagine also that when first aquired by your company the aircraft had a certificated weight of say 66 Tonnes.

Since they were not really using that landing weight the company then chose to re-certificate the aircraft to a lower max landing weight in order to save money. Guess what? The lower certificated landing weight now becomes the weight on which you are required to base your decisions.

So to summarise, last week you are not landing overweight, this week you are.

B2N2
6th Mar 2019, 17:28
Are you sure you're flying a T7?

Boeing does not prohibit an overweight autoland. They merely state in the AFM (which should be no different to the one you read) it is not recommended.
There is a distinct difference in how you paint the picture.
Cheerio!

Ok now you’re arguing about manufacturers recommendations.
Of it’s not recommended it should be avoided except in dire straits.
Which we’re not in this scenario.

FlightDetent
7th Mar 2019, 22:14
So to summarise, last week you are not landing overweight, this week you are. The problem there lies with the company policy, associated training and its application.

It is 2019, the manufacturers are ready to help and put all their knowledge and customers' operating wisdom into the guidelines already. If those are seen as vague it means getting more specific had drawbacks here and there that would be too impractical to deal with or undesirably restrictive. It is easy to to create policies for the calculated, but when the unforeseen arrives one could find himself missing tools needed for the job very easily.

For instance the article wiggy linked has all you need.
- staying inside the Operational Landing Limit {which is never higher than the structural) is a legal requirement
- there is no technical aspect preventing an overweigt landing. Extensive description how and why.
- as long as the landing performance works with standard landing flap (on the runway one just departed from it always does, by a factor 2,5 ish).


My short? The A/C is built per certification requirements to enable an overweight landing at MTOW. You foul nothing doing so, and reasoning around the legal aspect is the single remaining task.

If you need a more definite clause, inevitably the discussion stucks over the meanings of "needed", "ensure safety" "preferable" or similar. Terms that are subjective constructs and have no measurable meaning to begin with. Watch the other distinguished posters draw swords over "not recommended" and "non recommended". Both probably native English speakers and pilots.



agg_karan
8th Mar 2019, 02:35
As per our Ops manual, Eng failure is a MAY DAY call. The list also includes many others scenarios as well.
as per my understanding uttering MAYDAY Means now you are also time critical which would defeat the very purpose of the call if someone opted to jettison.

the only reason one would probably decide to reduce a/c weight either to Max landing or higher just enough to ensure adequate landing dist margins are avail at the Land ASAP airport.

I rather not get into back stage factors as to why the ops manual says MAYDAY for single engine, or climb gradient requirements of the approach you make or like some people say be extra safe and think of the tyres etc...

one thing would be certain that overweight landing and other relevant checklists will all be carried out in time before landing.

Yaw String
8th Mar 2019, 22:14
On the subject of MAYDAY/PANPANPAN or whatever you like ,remember one of the main reasons for giving this call as early as possible after the event. Its all about the biggest threat,and it's probably not to you!
What have you left on the runway,on that dark and dirty night,that the next departure may well hoover up!

casablanca
7th Apr 2019, 12:48
Both ways will probably have a safe outcome, I agree.
There are some companies that will support either way and not ever second guess you......there are also some companies that will say bring it back, land overweight, but God forbid you have a few fuse plugs melt, have hot brakes get welded to the axle or anything and it will all be "your fault"and you will be out the door..... Vapp at 345 tons is 201 kts, so good chance things will heat.

FlightDetent
7th Apr 2019, 13:24
What's the V2 with takeoff flap, casa? Do tell.

casablanca
7th Apr 2019, 20:37
Depends on number of factors but around 187?
have seen several RTOs that have caused damage due to hot brakes...
quite likely that doing flaps 20 approach due to 1 engine inop you will be over 200 kts. Hypothetically possible to exceed max tire speed of 204- which may warrant changing all tires, definitely be in the fuse plug melt zone, so strong possibility expensive repairs required...... “if” that happens I would wager many companies might say why didn’t you dump fuel????

FlightDetent
8th Apr 2019, 03:10
That really is a lot of E(k), in high PA environment.

Dave Therhino
9th Apr 2019, 09:03
A bunch of incorrect information on certification requirements has been written in this thread.

The regulation that determines whether a jettison system is required is 14 CFR 25.1001(a). It has nothing to do with the relationship between max takeoff weight and max landing weight. The requirement for a jettison system is instead based on climb capability at a weight equal to max takeoff weight minus the weight of fuel necessary for a 15 minute flight consisting of a takeoff and return to land. If the climb gradient requirements of sections 25.119 (all engine climb in the landing configuration flaps down gear down) and 25.121(d) (engine out climb in the approach configuration flaps down gear up) cannot be met at this weight, then a jettison system is required by 25.1001(a).

The flow performance of the jettison system, if required by 25.1001(a), is required by 25.1001(b) to be able to get the airplane within 15 additional minutes to a weight that allows the airplane to meet the climb gradient requirements of 25,119 and 25.121(d).

The braking system regulation, section 25.735, sets the energy absorption capability requirements for the brakes. Landing at max landing weight at anticipated speeds must be withstood repeatedly as normal operation with no damage other than normal wear. Landing at max takeoff weight must be withstood without hazard, but parts can be destroyed or require inspection/maintenance. The structural regulations (25.473) set the landing loads that must be met by setting descent rates that must be accommodated as limit loads at max takeoff weight (6 feet per second descent rate at touchdown) and at max landing weight (10 feet per second descent rate at touchdown). A design can be limited by the braking and structural regulations to a maximum landing weight that is significantly less than the maximum takeoff weight, and whether or not a jettison system is required would have nothing to do with this. It's all design choice - how strong do you want to build your gear and brakes, and what climb performance do you want to provide.

Of course, performance information (climb gradient and runway distance) for landings in excess of the maximum landing weight up to the max takeoff weight is required to be provided in the AFM by 25.1587(b)(3).

So yes, as most of you pilots already know, you can theoretically land safely above the maximum landing weight, but you are going to at least have some inspections required afterward, and worst case could blow the tires and damage the brakes and wheels. I am not qualified to speak about the judgment of whether you should do this in a real world situation.